Which statement about rods is true?

Which statement about rods is true?

• A. They are more sensitive to light and can signal the absorption of a single photon
• B. They are concentrated in the fovea
• C. They provide color vision
• D. They operate best in bright daylight

Answer: (A)

Rods are extremely sensitive photoreceptors that enable vision in very dim light. Each rod contains the pigment rhodopsin, and the phototransduction cascade amplifies even a single photon into a detectable electrical signal, so rods can signal the absorption of a single photon. They are located mainly in the peripheral retina, not in the fovea, which is rich in cones and geared toward high-acuity color vision in bright light. Cones provide color vision and function best in daylight, and the fovea is where they are concentrated. Because of their high sensitivity, rods drive vision under low illumination, making the statement about their ability to detect a single photon the correct one.

Rods are extremely sensitive photoreceptors that enable vision in very dim light. Each rod contains the pigment rhodopsin, and the phototransduction cascade amplifies even a single photon into a detectable electrical signal, so rods can signal the absorption of a single photon. They are located mainly in the peripheral retina, not in the fovea, which is rich in cones and geared toward high-acuity color vision in bright light. Cones provide color vision and function best in daylight, and the fovea is where they are concentrated. Because of their high sensitivity, rods drive vision under low illumination, making the statement about their ability to detect a single photon the correct one.